Thus, as argued previously (Plotnikov et al. 2019), the causal variant at the TSPAN10 locus appears to have a complex and somewhat paradoxical role in eye development, acting with a recessive mode of action as a major risk factor for strabismus and amblyopia—which often co-occurs with hyperopia—while also acting with an additive mode of action as a minor risk factor for a more myopic refractive error. Here, TSPAN10 is linked to amblyopia.